GCF (HCF) of 9 and 21
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What is the Greatest Common Divisor of 9 and 21?
Answer
GCF (HCF) of 9 and 21 is
3
Common factors: 1, 3
3 divides both: 9 ÷ 3 = 3, 21 ÷ 3 = 7 — and 3 and 7 share no factor but 1, so no larger number divides both.
9 = 32
21 = 3 × 7
| Prime | 9 | 21 | Lowest power |
|---|---|---|---|
| 3 | 32 | 3 | 3 |
| 7 | — | 7 | — |
— = power 0: the prime is not a factor of this number, so it cannot be in the GCF.
GCF = 3
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See Also
- Least Common Multiple - Find the Least Common Multiple (LCM) of two numbers
- Greatest Common Factor of 3 Numbers - Find the Greatest Common Factor (GCF) of three numbers
- Least Common Multiple of 3 Numbers - Find the Least Common Multiple (LCM) of three numbers
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